Darn shame that all of the regions taken so far amount to like 300 more gold and 200 more food. This is a huge exercise in futility that my restless nobles prodded me into doing. 
Like egamma said, it keeps the borders clear at least.
The interesting thing about the new system is that you can appoint one person as Duke over the entire area, have them collect 50% of the taxes from all the regions, and get a fairly decent income that way. No need to worry about food--there's not enough to both with, either positive or negative.
